Aqua-Hot AHE-200-02S-24 VDC Installation Guide download pdf (Page 30)

3.2.3. Earthing

The following basic issues need to be considered when installing a frequency converter, so as to

obtain electromagnetic compatibility (EMC).

• Safety earthing: Please note that the frequency converter has a high leakage current and

must be earthed appropriately for safety reasons. Apply local safety regulations.

• High-frequency earthing: Keep the earth wire connections as short as possible.

Connect the different earth systems at the lowest possible conductor impedance. The lowest pos-

sible conductor impedance is obtained by keeping the conductor as short as possible and by using

the greatest possible surface area.

The metal cabinets of the different devices are mounted on the cabinet rear plate using the lowest

possible HF impedance. This avoids having different HF voltages for the individual devices and

avoids the risk of radio interference currents running in connection cables that may be used be-

tween the devices. The radio interference will have been reduced.

In order to obtain a low HF impedance, use the fastening bolts of the devices as HF connection

to the rear plate. It is necessary to remove insulating paint or similar from the fastening points.

3.2.4. Extra Protection (RCD)

ELCB relays, multiple protective earthing or earthing can be used as extra protection, provided

that local safety regulations are complied with.

In the case of an earth fault, a DC content may develop in the faulty current.

If ELCB relays are used, local regulations must be observed. Relays must be suitable for protection

of 3-phase equipment with a bridge rectifier and for a brief discharge on power-up.

See also the section

Special Conditions

in the relevant Design Guide.

3.2.5. RFI Switch

Mains supply isolated from earth:

If the frequency converter is supplied from an isolated mains source (IT mains, floating delta and

grounded delta) or TT/TN-S mains with grounded leg, the RFI switch is recommended to be turned

off (OFF)

. For further reference, see IEC 364-3. In case optimum EMC performance is needed,

parallel motors are connected or the motor cable length is above 25 m, it is recommended to set

the switch in ON position.

In OFF position, the internal RFI capacities (filter capacitors) between the chassis and the inter-

mediate circuit are cut off to avoid damage to the intermediate circuit and to reduce the earth

capacity currents (according to IEC 61800-3).

Please also refer to the application note

VLT on IT mains

, MN.90.CX.02. It is important to use

isolation monitors that are capable for use together with power electronics (IEC 61557-8).

The RFI switch is not to be operated with mains connected to the unit. Check that

the mains supply has been disconnected before operating the RFI switch.

Open RFI switch is only allowed at factory set switching frequencies.

3. Installation

VLT

5000/6000/8000

High Power Installation Guide

MI.90.J2.02 - VLT

is a registered Danfoss trademark

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